(1) Field of the Invention
This invention relates to a semiconductor wafer test fixture and to methods for analyzing ultratrace amount of impurities in thin films present on the surface of the semiconductor wafer.
(2) Description of the Prior Art
The present means of chemically analyzing the chemical composition of thin films is destructive to the semiconductor wafer on which the thin films are located. A fixed area die is cut from the wafer, the thin films on the die is etched and this liquid transferred with extreme care to another vessel. The fluid is diluted and then the chemical nature of the thin film is determined with a chromatograph.
The book entitled "VLSI TECHNOLOGY" Second Edition by S. M. Sze published by McGraw-Hill International Editions, New York, N.Y., 1988 in its Chapter 12.4 pages 548-554 describes the use of chromatography and preparation of samples therefor. The U.S. Pat. No. 4,584,886 describes a method where silicon oxide or nitride films on wafers are dissolved with hydrofluoric acid and the solution collected and then sent to be checked for impurities in atomic absorption spectrophotometer. Other patents U.S. Pat. No. 3,976,377 and U.S. Pat. No. 3,824,016 describe other testing methods for semiconductor wafers. None of these publications provide accurate, fast, and safe methods or fixtures that allow wafer to be reused, i.e. that there is no requirement for dicing of the wafer.